Receivers for copies exiting from office copiers often include sorting machines which function to arrange the copies in discreet, collated sets. Examples of sorting machines having moving bins or moving bin openers to enlarge the space between receiver trays are well known in the prior art. Examples are shown in various prior United States patents including Lawrence U.S. Pat. No. 4,343,463, Du Bois U.S. Pat. No. 4,478,406 and U.S. Pat. No. 4,328,963, Stemmle U.S. Pat. No. 3,848,868, Schultz and Shirahase U.S. Pat. No. 3,879,032. There are numerous other examples in the prior art of sorters having means to open pivoted bins. Langner U.S. Pat. No. 4,265,445 is an example of sorters wherein the trays are fixed, but a pivoted infeed directs sheets to a selected bin.
Such sorting devices are well suited to the sequential operation employed in bi-directional sorting of multiple copies of original documents made on an office copying machine. The time interval between copies is adequate to allow movement of the bins or the bin openers from one tray to the next sub-jacent or super-jacent tray to collate copies from the low speed to mid-speed copiers, say, up to sixty or more, copies per minute.
With the advent of copying machines which function as printers, i.e., non-impact or electronic or laser printers which employ programmed imaging of a xerographic drum instead of photo-imaging of a hard original, the need has arisen for random access receivers. Such printers normally produce documents in sets, with the pages collated. However, the need exists for mailboxing of different jobs, as well as separation of sets. While set separation can be readily accomplished by feeding the pages of each set into the bins in sequence, mailboxing is more difficult, because the documents or jobs destined for different mailboxes may not and most likely will not be processed in sequence. Thus, mailboxing requires random access or positioning of the sheet feed for delivery to a selected bin or mailbox.
Where high speed, high volume printers are employed, relatively large, costly and complicated random access devices may be employed, such as those shown in Lawrence U.S. Pat. Nos. 4,343,463, or 819,969 as examples, where sheets are gated into a selected bin from or by a sheet transport.
Theoretically, the prior bin opening sorter devices identified above are also useful as mailboxing devices, but the rapid movement of the bins shifting or bin opening mechanisms required in the case of random access of the sheets to the trays poses a timing problem and a mechanical problem of rapidly accelerating the operating mechanism from, say, the first bin to the last bin and back, to separate two successive jobs.
Moreover, the vast majority of the non-impact or electronic printers using xerographic production of the image on the sheets, are small and relatively inexpensive, so that large and expensive or complicated mailboxing devices are not acceptable. While the sorter of Du Bois U.S. Pat. No. 4,328,963 referred to above is useful as a mailbox in conjunction with certain lower speed printers, because of the relatively large sheet capacity per bin for its overall size, such mailboxes are subject to excessive mechanical wear when the bin opening cam is made to move rapidly up and down the trays, while opening each tray in sequence when sheets are to be delivered in a random fashion, and, moreover, such mechanical motion imposes limitations on the sheet delivery speed of a printer with which such sorter is employed in a random access or mailbox fashion.